a. Structure and function of HIV-1 Rev response element (RRE). In collaboration with Dr. Yun-Xing Wang, we have analyzed the structure and function of the HIV-1 RRE, an RNA element required for the export of unspliced viral RNAs from the nucleus. Dr. Wang's group showed by small-angle x-ray scattering that the RRE has an A shape, with the two primary Rev binding sites facing each other at a distance of 55 Angstroms. We optimized the assay for Rev-RRE function and showed that this shape and the spacing are both essential for proper RRE functionality. _____b. Testing breast cancer samples for retroviruses. In collaboration with Dr. Edward Gabrielson (Johns Hopkins Medical Institution), we have developed sensitive assays for the presence of mouse mammary tumor virus-related sequences in human breast cancers. _____c. Function of MLV glycoGag. MLVs and other gammaretroviruses encode a glycosylated form of the Gag protein, termed glycoGag. The function of this protein is not known, although there are a number of hypotheses in the literature. We are testing several of these hypotheses. Our results to date show that glycoGag has a very significant effect on the infectivity of an MLV virus particle if the particle is carrying some Env proteins, but not if it carries others. We are determining the stage in the replication cycle at which glycoGag-deficient MLV particles are blocked. _____Patents Linked to Project: U.S. Patent #7,572,828: Identification of Anti-HIV Compounds Inhibiting Virus Assembly and Binding of Nucleocapsid Protein to Nucleic Acid; issued August 11, 2009; Robert Shoemaker, Michael Currens, Alan Rein, Ya Xiong Feng, Robert Fisher, Andrew Stephen, Shizuko Sei, Bruce Crise, Louis Henderson, and Karen Worthy. This patent describes a class of compounds with anti-HIV-1 activity, which are under investigation for use in antiretroviral therapy. Patent pending: 03773233.6 (EP application). _____[Corresponds to Rein Project 4 in the October 2011 site visit report of the HIV Drug Resistance Program (renamed HIV Dynamics and Replication Program in 2015)]